I Replaced AC blower Motor and Resistor - Questions

[9dawgs]

My AC blower went out a couple of weeks ago and I read up on the procedures here and over at Matthew's Volvo Site about how to replace the blower motor and resistor. I removed and replaced the offending units and everything was great for about a day. I drove the car to work, AC blowing strong, went to lunch and back with the same good strong AC function. Got in the car to come home and the blower would not work. Nothing, zilch, nada... So, I sent an email off to the vendor of the parts and they sent me a new resistor. The one I pulled out looked like the first one I removed as they both now have a burnt pin in the same position (see photos).

So my question are, before I power it up again:
1. What is the voltage to the resistor supposed to be at the connector?
2. If it is being given an over voltage, what would be the cause without a fuse burning out first?
3. Could this just have been a bad (new) resistor?

Ok, thanks for the quick reply. I need this AC. It has been crazy hot and humid here in Central Florida, not to mention the daily afternoon rain storms.

[hoonk]

they both now have a burnt pin in the same position

Could this just have been a bad (new) resistor?

The melted pin is from a bad connection. The female portion of the spade connector was loose on the old and new (and new again) male spade connector in the resistor. After female spade connectors are overheated they loose their "springyness", and won't fit tight enough to prevent heat buildup from a bad connection - The best repair will be to replace the female spade connector with a new one. You may have to find a connector like that cut from a wire harness at a junkyard - or cut that part of the connector off and plug that wire in by itself (with a new spade terminal)

[9dawgs]

Ahh, so no over voltage then. I'll check for a replacement. Thanks for the tip! And quick response :>)

[9dawgs]

The melted pin is from a bad connection. The female portion of the spade connector was loose on the old and new (and new again) male spade connector in the resistor. After female spade connectors are overheated they loose their "springyness", and won't fit tight enough to prevent heat buildup from a bad connection - The best repair will be to replace the female spade connector with a new one. You may have to find a connector like that cut from a wire harness at a junkyard - or cut that part of the connector off and plug that wire in by itself (with a new spade terminal)

How would I remove the female end from the connector to clean it up and tighten up the "grip"? I normally would use a small jeweler's screwdriver and depress the catch at the top of the female end and slide it out of the back of the connector. It's not working on this one. When I push the screwdriver in the slot above the female end the white piece thats inserted in the connector slides forward but not out. This does nothing to release any of the connectors.

[Willy]

I don't want to shed any doubt on hoonks reply, but just in case the problem isn't solved:
I don't think the fan speed is governed by a resistor, but rather by a transistor (possibly
a darlington couple: one high gain, one high current, together both), the Fan Control Module.
What can happen is that, if the cabin filter is clogged, the fan will draw a very high current
to obtain a decent air flow. This current flows through the FCM which gets hot. It is cooled
by the air from the fan, but that doesn't work as it should be because the air can't flow since
the filter is clogged. The result is that the FCM burns/fails.
It is a known problem that the FCM can fail if the cabin filter hasn't been replaced for a long time.
I can't say that this is what happens in your car, it is merely a possibility.
The FCM works on the car's supply voltage, 12VDC. At the connector is a direct (fan can blow if
car is shut-down) 12V connection. If I am not mistaken, the fuse is 30A. The FCM will probably
fail to open circuit before the fuse blows.
Of course this is just guesswork, it is certainly possible that the FCM you received was a bad one,
although it did work for a short while.
Willy

[hoonk]

How would I remove the female end from the connector to clean it up and tighten up the "grip"?

I would not try to tighten an overheated spade terminal that has lost it's tension. (you can't put the spring back in a melted spring by bending it) Have had too many come back (with irritated customers). I would replace the terminal. You may have to cut the corner of the plastic terminal holder off to be able get the wire out and crimp a generic spade terminal on the wire. Or Source a (good) used piece of harness from a junk Volvo and splice in what you need.

The fans can and do sometimes draw too much current - in that case the control unit shuts off the current flow to the fan.

[9dawgs]

I don't want to shed any doubt on hoonks reply, but just in case the problem isn't solved:
I don't think the fan speed is governed by a resistor, but rather by a transistor (possibly
a darlington couple: one high gain, one high current, together both), the Fan Control Module.
What can happen is that, if the cabin filter is clogged, the fan will draw a very high current
to obtain a decent air flow. This current flows through the FCM which gets hot. It is cooled
by the air from the fan, but that doesn't work as it should be because the air can't flow since
the filter is clogged. The result is that the FCM burns/fails.
It is a known problem that the FCM can fail if the cabin filter hasn't been replaced for a long time.
I can't say that this is what happens in your car, it is merely a possibility.
The FCM works on the car's supply voltage, 12VDC. At the connector is a direct (fan can blow if
car is shut-down) 12V connection. If I am not mistaken, the fuse is 30A. The FCM will probably
fail to open circuit before the fuse blows.
Of course this is just guesswork, it is certainly possible that the FCM you received was a bad one,
although it did work for a short while.
Willy

I replaced the cabin filter when I replaced the original fan and resistor. Good thought though, thanks for your input.

[9dawgs]

I would not try to tighten an overheated spade terminal that has lost it's tension. (you can't put the spring back in a melted spring by bending it) Have had too many come back (with irritated customers). I would replace the terminal. You may have to cut the corner of the plastic terminal holder off to be able get the wire out and crimp a generic spade terminal on the wire. Or Source a (good) used piece of harness from a junk Volvo and splice in what you need.

The fans can and do sometimes draw too much current - in that case the control unit shuts off the current flow to the fan.

True, I took the connector apart at the trouble site. I then cleaned the inside with a sliver of an emery board and then squeezed it tighter with a pair of needle nosed pliers and plugged it back in. I made sure the spade was secure. I drove it to work this morning to see what will happen. So far so good. I'm heading to the junk yard this week to try and locate a good plug.

Worse case, the resistor will burn out again and I'll just have to start all over. It's really not too bad of a job. I'm actually getting pretty good at it :>P It's just really hot outside right now so my tools get sweaty.

Thanks again for your input on this. It really helped.

[Willy]

Perhaps it is possible to bens or twist the pin a little so that it makes at least contact on some of its surface.
Willy

[9dawgs]

Perhaps it is possible to bens or twist the pin a little so that it makes at least contact on some of its surface.
Willy

Yeah it seems like it's holding up well. I disassembled the old fan motor plug yesterday to try and salvage the female spade. I figure if it went out again I could splice it into the existing wire and plug it back in. In the meantime I've ordered a pigtail with a new(used) plug from Voluparts Inc. for $15 including shipping. The salvage yard didn't have any good donor Volvo's to scavenge. When it gets here I'll just splice it into the wiring and should be good to go.

Thanks again for all the help on this.

My biggest issue to start was removing the spade from the plug housing. Just an FYI for anyone who needs to do this (see image below), to remove the spade from the back of the housing you have to pull the white part forward and out (it only comes out about 1/8 inch) from the front of the housing and then insert a small flat blade jewelers screwdriver into the tiny gap on top of the spade you want to remove making sure to point the blade down to release the plastic catch at the top of the spade and then simply pull the wire out of the back of the housing. If your spade was burnt like mine then it will take a bit of effort to wiggle it out of the burnt plastic. The image in the photo is the 2 spade fan connector but it has the same disassembly procedure as the 4 spade resistor plug. I just couldn't find a photo online of the 4 spade and I didn't get a photo of mine. Hope this helps someone.